A method of this general type is known from German Pat. No. 977,886 of the applicant and is of proven value, especially in the compensation of so-called non-magnetic articles. What is meant by this are articles and apparatus of largely non-magnetic design, i.e., combustion engines or electric motors in non-magnetic housings, such as are frequently intended for installation in ships or tanks.
Because of the danger or triggering magnetic mines or other magnetically controlled weapons, it is often necessary to keep the interference caused by the earth's magnetic field in the vicinity of vehicles of this type as low as possible. In this connection, for reasons which are explained in detail in the above-cited patent, the vertical component of the earth's magnetic field plays a decisive role. Special measures for suppressing the magnetic interference field produced from the vertical component of the earth's field on ferromagnetic components therefore is often necessary. In the above-mentioned engines or motors with housings of non-magnetic material, each individual ferromagnetic component of the engine or motor, such as tie-bars, cylinder head screws, etc., was compensated according to the above-mentioned patent prior to being installed in the non-magnetic housing.
To accomplish this, the component to be compensated was first demagnetized in a zero field to remove any permanent magnetization present. The zero field was produced by eliminating the earth's magnetic field in the vicinity of the component by means of a wire loop producing an appropriately dimensioned opposite field. The component was then placed in contact with a permanent magnet, whose magnetic moment was opposed to the moment induced in the component from the vertical components of the earth's field and dimensioned in such a manner as to result in an overcompensation. Then, the component was subjected to the influence of a decaying alternating magnetic field while the component was located in its normal position within the earth's magnetic field. Under the influence of this decaying alternating field, which anticipates the subsequent mechanical vibration of the component, the permanent magnetization of the component changed in the direction of the idealization curve, i.e., became greater, under the influence of the vertical component of the earth's field, so that with the stabilized magnetization value now achieved, approximate compensation through the permanent magnets was produced. If the compensation was still not sufficient, the treatment in the decaying alternating magnetic field was repeated with a somewhat greater initial amplitude of the alternating field. In this connection, it was only necessary to insure that the initial field amplitude was always large enough to correspond to the maximum mechanical vibration expected in actual service. The components compensated with high stability in this manner were then installed in the non-magnetic housing.
However it has so far not been possible to provide stable compensation of the vertical components of the magnetization of combustion engines, which are fabricated entirely of steel and which also have a housing of cast steel.